Q12 of 90 Page 33

Calculate using appropriate algebraic identity:

(– 15)3 + (28)3 + (– 13)3


[Hint: Use the identity : If x + y + z = 0 the x3 + y3 + z3 = 3xyz]

Here, (x + y + z) = (– 15 + 28 – 13) = 0

Now, using the identity:


If x + y + z = 0, then x3 + y3 + z3 = 3xyz


⇒ (– 15)3 + (20)3 + (– 13)3 = 3(– 15)(28)(– 13)


= 16380


More from this chapter

All 90 →
10

Verify that:

x3 + y3 + z3 – 3xyz = 1/2 (x + y + z)[(x – y)2 + (y – z)2 + (z – x)2]

 10

Verify that:

27a3 + b3 + c3 – 9abc = (3a + b + c)[3a2 + b2 + c2 – 3ab – bc – 3ac]

 11

If x + y + z = 0 then verify that x3 + y3 + z3 = 3xyz.

 12

Calculate using appropriate algebraic identity:

(30)3 + (20)3 + (– 50)3